An exemplary embodiment of the inventive concept relates to a phase change random access memory device and methods of manufacturing and operating the same.
A phase change random access memory (PRAM) device is a memory device which stores binary data ‘0’ and ‘1’ through a change in electrical resistance values between a crystalline state of the PRAM and an amorphous state of the PRAM. To change the state of the PRAM device from a crystalline state to an amorphous state, an electrical current is applied to the PRAM device to generate sufficient Joule heat to melt a portion of phase change material. The electrical current is referred as a reset current.
One of the most important factors toward the development of high-integration PRAM devices is reduction of the reset current. Methods of reducing the reset current include employing a method of increasing the resistance of a bottom electrode contact (BEC) by changing its composition, and by employing a ring-shaped BEC.
According to these methods, high-Joule heat may be generated, and, at the same time, the reset current can be reduced. However, these methods also increase the electrical resistance of the PRAM device in a set state. Thus, the ratio of the reset resistance to the set resistance may decrease. In this case, the sensing margin for reading data becomes smaller. Thus, it may be more difficult to determine whether the read data is ‘1’ or ‘0’, which can lead to device malfunction.